A case of a single coronary artery arising from the right coronary cusp

Coronary artery anomalies (CAAs) are present in 1-1.96% of the population [1,2]. The clinical significance of single CAAs differs depending on the course of the artery. Those that take an inter-arterial (malignant) course, between the aorta and pulmonary artery, can present with syncope or sudden death [1,3]. This is attributed to the myocardial ischaemia that ensues when the single coronary artery is compressed between high-flow structures in systole. Whereas, those that traverse benign, inter-ventricular paths do not predispose to myocardial ischaemia, hence, patients are often asymptomatic [1,3].

Image 1: Right Coronary Artery

Image 2: Left Main Stem arising from Right Coronary Cusp

Image 3: The interventricular course of the LMS and bifurcation into LAD and Cx

These computed tomography maximum intensity projection images show a single coronary artery (SCA) arising from the right coronary cusp in a 68 year old male patient who presented with atypical chest pain. This specific anomaly is rare, with a prevalence of 0.004 - 0.05% [2,4]. Images 1 and 2 show the right coronary artery (RCA) and left main stem (LMS) arising from the right coronary cusp (RCC). In anatomically normal coronary circulations, the LMS arises from the left coronary cusp, shortly after which, it bifurcates to give the left anterior descending (LAD) and circumflex (Cx) arteries, that supply the left ventricle (LV). Image 3 shows the long, benign, inter-ventricular course of the LMS, and its bifurcation into LAD and Cx, both of which contain calcified eccentric plaques. According the Lipton classification system [5], this represents a R-II S single coronary artery anomaly, on account of its origin at the right coronary sinus and the initial common trunk that bifurcates to give the RCA and long inter-ventricular LMS. Myocardial tunneling was apparent in the LMS, however, this did not compromise blood flow in the vessel at rest. Mixed plaque disease causing moderate to severe stenosis of the RCA is noted in Image 2.

Given the benign course of the SCA in this case, it is likely that the presentation with atypical chest pain results from significant coronary artery atheromatous disease. Despite this, knowledge of the anomalous coronary artery anatomy in this patient is of considerable value should he later require invasive treatment for his coronary artery disease.